Thioamides, their preparation and uses

ABSTRACT

The froth flotation of a metal sulfide mineral is carried out using a thioamide as the collector in which the thioamide is of the formula ##STR1## R designating C 5  to C 17  alkyls, R&#39; being H or (CH 2 ) n  OR&#34; and n an integer of 1 to 6, while Z is --OR&#34; or ##STR2## where R&#34; means H, CH 3  or C 2  H 5 .

This is a continuation-in-part of application Ser. No. 632,630, filedJuly 19, 1984 now abandoned.

The invention relates to thioamides carrying a second function. Itincludes the use of such amides as collectors in the flotation ofminerals. The invention also relates to certain new thioamides carryinga second function, as well as to a process for their preparation.

Thioamides have various industrial uses, for example as additives incosmetic and pharmaceutical compositions, lubricating oil improvers,fungicides, vulcanization accelerators etc; they can also be used ascollectors in the froth flotation of metal sulfide minerals such as, forexample, galena, blende and pyrites. Flotation is carried out in theconventional fashion using a thioamide as the collector. The thioamidesare of the formula ##STR3## R designating C₅ to C₁₇ alkyls, R' being Hor (CH₂)_(n) OR" and n an integer of 1 to 6, while Z is --OR" or##STR4## where R" means H, CH₃ or C₂ H₅.

The preferred manner of preparing the thioamide involves dissolving thethioester in a suitable solvent, which can be a chlorinated hydrocarbon,for example dichloromethane, dichloroethane, trichloroethane,trichloroethylene, tetrahydrofuran or other solvent inert as regards thereactants present; to the solution obtained, the selected amine isadded, if required in a slight excess. The reaction is allowed toproceed during the necessary time, which varies with the nature of thereactants, but is generally from 1/2 to 6 hours. The temperature is from0 degrees to 50 degrees C. and, preferably, between 0 degrees and 25degrees C., except when R is a halogenated aryl group, in which case thepreferred temperature is of the order of 40 degrees C.

Using this process, a series of new compounds have been prepared, withinthe scope of the present invention, constituted by thioamides which canbe represented by the formula: ##STR5## R designating C₅ to C₁₇ alkyls,R' being H or (CH₂)_(n) OR" and n an integer of 1 to 6, while Z is --OR"or ##STR6## where R" means H, CH₃ or C₂ H₅. Preferably, R is a C₇ to C₁₁linear alkyl group.

In the non-limitative examples which follow, the preparation of severalof the products defined above is described. The physical properties ofthese compounds are set out in a Table at the end of the Examples. Thesethioamides and their homologues are utilizable successfully for theseparation of minerals, particularly sulphur-containing minerals, byflotation.

EXAMPLES 1 TO 4 Synthesis of N-(2-hydroxyethyl)thiocarbamide

First a solution is prepared of 0.5 mole of the ethyl dithioate,R--CS--SC₂ H₅, (where R is indicated below) in 100 ml ofdichloromethane. 0.5 mole of ethanolamine, NH₂ CH₂ CH₂ OH, is thenadded, with agitation, to the solution obtained. The mixture is allowedto stand at 25° C. for 3 hours. The solvent is then evaporated and theresidue is crystallized and then re-purified by re-crystallization fromhexane, containing a trace of a polar solvent, particularlydichloromethane.

With this mode of operation, there have been prepared:

Ex. 1: R being C₁₁ H₂₃, N-(2-hydroxyethyl)thiododecanamide CH₃ (CH₂)₁₀CS--NH--CH₂ CH₂ OH. in a yield of 86%.

Ex. 2: R being C₆ H₅, N-(2-hydroxyethyl)thiobenzamide C₆ H₅--CS--NH--CH₂ CH₂ OH in a yield of 45%.

Ex. 3: R being CH₃ O--C₆ H₄, N-(2-hydroxyethyl)-4-methoxy-thiobenzamideCH₃ O--C₆ H₄ --CS--NH--CH₂ CH₂ OH in a yield of 84%.

Ex. 4: R being CH₃ C₆ H₄, N-(2-hydroxyethyl)-4-methyl-thiobenzamide CH₃--C₆ H₄ --CS--NH--CH₂ CH₂ OH in a yield of 69%.

EXAMPLE 5 Preparation of N-(3-aminopropyl)thiododecanamide

10.4 g of ethyl-dodecanedithioate is dissolved in 100 ml of toluene andthe solution obtained is mixed with a solution of 30 g of1,3-diaminopropane in 200 ml of toluene. The mixture is maintained atabout 10° C. for 1 hour, with stirring.

The toluene is then distilled off under reduced pressure; the excessamine is eliminated by distillation. After recrystallization of theresidue from hexane, pure N-(3-aminopropyl)dodecanethioamide, CH₃(CH₂)₁₀ --CS--NH--CH₂ CH₂ CH₂ NH₂, is obtained in a yield of 45%.

EXAMPLES 6 TO 10 Preparation of N-(6-aminohexyl)thioamides

The operative mode consists of adding 0.5 mole of the selected alkyldithioate R--CS--SR', diluted with 100 ml of toluene, to 200 ml of atoluene solution of 0.5 mole of 1,6-diaminohexane.

The disappearance of the colour of the thioester allows the reaction tobe followed; this is generally terminated after 30 minutes at 25° C.Exceptionally, in the case of Example 9, 1 hour at 40° C. was required.The toluene and the major part of the excess amine are eliminated bydistillation under reduced pressure, in order to be re-used in a newpreparation after separation of the mercaptan formed. The residue fromthe distillation is washed with a small quantity of water, which causeselimination of the remaining amine.

For the compounds below, the residue was redissolved in toluene and dryHCl gas was passed into the solution obtained, thus causingprecipitation of the hydrochloride of the thioamide formed.

    __________________________________________________________________________                                     % Yield based on                             Ex. No                                                                            Thioester used                                                                             Thioamide obtained                                                                            the thioester                                __________________________________________________________________________    6   Ethyl decanedithioate                                                                      C.sub.9 H.sub.19 CSNH(CH.sub.2).sub.6 NH.sub.2.HCl                                            91                                           7   Methyl benzenedithioate                                                                    C.sub.6 H.sub.5 CSNH(CH.sub.2).sub.6 NH.sub.2.HCl                                             62                                           8   Ethyl-para-methoxy- benzene-dithioate                                                       ##STR7##       64                                           9   Ethyl-para-chloro- benzene dithioate                                                        ##STR8##       25                                           10  Methyl-para-methyl- benzene dithioate                                                       ##STR9##       67                                           __________________________________________________________________________

Similar results are obtained starting from the corresponding monothioicesters: R--C^(S) --OR'.

EXAMPLES 11 AND 12 Thioamides of N-(2-dimethylamino-ethane)

The operative mode of the foregoing Examples is used withN,N-dimethylethylenediamine, (CH₃)₂ N--CH₂ CH₂ --NH₂, which is reactedwith an O-alkyl thioester R--CS--OR'.

11. The thioester employed, ethyl decanethioate, CH₃ (CH₂)₈ --CS--OC₂H₅, gives N-(2-dimethylamino-ethyl)-thiodecanamide, ##STR10## in a yieldof 81%. The same result is obtained starting from ethyl decanedithioateCH₃ (CH₂)₈ CS--SC₂ H₅.

12. Starting with ethyl para-chlorobenzenedithioate, Cl--C₆ H₄ CS--SC₂H₅, N-(2-dimethylamino-ethyl)-4-chlorothiobenzamide, ##STR11## isobtained, the yield being 68%.

EXAMPLES 13 & 14 Preparation of N-(2,2-dimethoxyethyl)thioamides

Operation is as in Examples 1 to 4, but with ethanolamine replaced by2,2-dimethoxyethylamine, ##STR12## which leads to thioamides carryingacetal functions, as follows: 13. Starting from the ethyl ester ofdecanethioic acid, C₉ H₁₉ CS--OC₂ H₅,N-(2,2-dimethoxyethyl-)thiodecanamide, ##STR13## is obtained. 14.Starting from ethyl p.chloro-benzene-dithioate,N-(2,2-dimethoxyethyl)-4-chlorothiobenzamide, ##STR14## is made, in ayield of 57%.

EXAMPLE 15 Preparation of a thioamide having a carboxyl function

The amine utilized here is an amino acid. 0.2 mole of DL-alanine,##STR15## is added in small portions to 300 ml of a 10% aqueous solutionof NaOH in which has been dissolved 0.2 mole of methyl octanedithioate,CH₃ (CH₂)₆ CS--SCH₃. The mixture is maintained at the ambienttemperature for 15 hours. It is then acidified with 300 ml of 20%aqueous HCl acid, which causes precipitation of the thioamide formed.The latter is purified by recrystallization from hexane containing aslight amount of ether. N-(2-carboxyethyl)thio-octamide, ##STR16## isthus obtained in a yield of 76% in relation to the thioester used.

EXAMPLES 16 TO 18 Thioamides carrying a pyridyl group

The selected dithioesters are reacted with 2-aminomethylpyridine (orα-amino-picoline) ##STR17## following the technique of Examples 1 to 4.

The dithioesters utilised are respectively those of Examples 8, 9 and 10indicated above and the following thioamides are obtained:

16. N-(2-pyridylmethyl)-4-methoxythiobenzamide, ##STR18## in a 60%yield. 17. N-(2-pyridylmethyl)-4-chlorothiobenzamide, in a 54% yield.

18. N-(2-pyridylmethyl)-4-methylthiobenzamide, in a 58% yield.

EXAMPLE 19 Preparation of a thioamide carrying two hydroxyl substituentson the nitrogen, particularly N-bis(2-hydroxyethyl)dodecanethioamide,##STR19##

The mixture of 0.2 mole of ethyl dodecanedithioate with 0.24 mole ofdiethanolamine is heated to 160° C. for 30 minutes. After cooling, anequal volume of water is added; the whole is then cooled to causeseparation of an oil; this treatment is renewable to eliminate theexcess diethanolamine.

The thioamide obtained, having the formula given above, is an oilslightly soluble in water. The operative conditions are similar to thoseused with the other dialkanolamines.

EXAMPLE 20 Production of a thioamide having a carboxyl group on thenitrogen.

18 g of 2-aminopropionic acid (β-alanine) is dissolved in 100 ml of 10%aqueous caustic soda; 21 g of ethyl octanedithioate in 200 ml oftetrahydrofuran is then added; the mixture is agitated for 48 hours andthen the organic solvent is distilled off. After cooling, the mixture isacidified with 200 ml of 20% hydrochloric acid; the precipitate whichforms is separated and then washed with 1% HCl and with water. Afterdrying, it can be recrystallized from toluene.

    CH.sub.3 --(CH.sub.2).sub.6 --CS--NH--CH.sub.2 CH.sub.2 --CO.sub.2 H Yield 73%

    __________________________________________________________________________     ##STR20##                                                                    Ex. no                                                                            R        R"        Z          MP °C.                               __________________________________________________________________________    1   CH.sub.3 (CH.sub.2).sub.10                                                             CH.sub.2 CH.sub.2                                                                       OH         53                                          2   C.sub.6 H.sub.5                                                                        "         "          94                                          3   CH.sub.3 OC.sub.6 H.sub.4                                                              "         "          97                                          4   CH.sub.3 C.sub.6 H.sub.4                                                               "         "          122                                         5   CH.sub.3 (CH.sub.2).sub.10                                                             CH.sub.2 CH.sub.2 CH.sub.2                                                              NH.sub.2   104                                         6   CH.sub.3 (CH.sub.2).sub.8                                                              (CH.sub.2).sub.6                                                                        NH.sub.2.HCl                                                                             168                                         7   C.sub.6 H.sub.5                                                                        "         "          125                                         8   p.CH.sub.3 OC.sub.6 H.sub.4                                                            "         "          179                                         9   p.ClC.sub.6 H.sub.4                                                                    "         "          173                                         10  p.CH.sub.3C.sub.6 H.sub.4                                                              "         "          155                                         11  CH.sub.3 (CH.sub.2).sub.8                                                              CH.sub.2 CH.sub.2                                                                        ##STR21## 38                                          12  p.ClC.sub.6 H.sub.4                                                                    "         "          82                                          13  CH.sub.3 (CH.sub.2).sub.8                                                              CH.sub.2                                                                                 ##STR22## 22                                          14  p.ClC.sub.6 H.sub.4                                                                    "         "          34                                          15  CH.sub.3 (CH.sub.2).sub.6                                                               ##STR23##                                                                              COOH       Decomp.                                     16  p.CH.sub.3 OC.sub.6 H.sub.4                                                            CH.sub.2                                                                                 ##STR24## 94                                          17  p.ClC.sub.6 H.sub.4                                                                    CH.sub.2                                                                                 ##STR25## 106                                         18  p.CH.sub.3C.sub.6 H.sub.4                                                              "         "          81                                          19  CH.sub.3 (CH.sub.2).sub.10                                                             "                                                                                        ##STR26## oil                                         20  CH.sub.3 (CH.sub.2).sub.6                                                              CH.sub.2 CH.sub.2                                                                       COOH       93                                          __________________________________________________________________________

The thioamides according to the invention are suitable for the usualuses of thioamides. They can be utilized for the protection of plantsagainst parasites. In an interesting application, the thioamide servesas the collector for the flotation of minerals, as illustrated byExample 21 below.

EXAMPLE 21

Flotation tests in a HALLIMOND cell are effected in the standard manner,described in French published patent No. 2429613, page 3, lines 26 to40. The collector employed is N-bis(2-hydroxyethyl)dodecanethioamide ofExample 19 given above. It is utilized in a 1% ethanolic solution at therate of 100 g of collector per tonne of mineral.

The percentages of the minerals flotated at different pH values are asfollows:

    ______________________________________                                        pH      Galena         Blende  Pyrites                                        ______________________________________                                        5.5      93%            82%     40%                                           7.02    91             80      56                                             9.01    84             13      23                                             10.5    82             12      11                                             ______________________________________                                    

It can be seen that up to pH 7 the results with galena are remarkableand they are very good with blende. Starting at pH 9, the separation ofthese two minerals is very easy. The thioamide also proves to be usefulfor the separation of pyrites. This collector is also suitable in thecase of chalcopyrite.

EXAMPLES 22 by 37

Flotation tests were carried out in the manner described in Example 21with various thioamides belonging to the group of compounds having theformula ##STR27## the pulp of the mineral treated having the pH 6.7.

    ______________________________________                                        N°  Alkyl       % of mineral recovered                                 Example    R       n       galena  blende                                     ______________________________________                                        22         C.sub.3 H.sub.7                                                                       2       63      58                                         23         C.sub.4 H.sub.9                                                                       2       67      58                                         24         C.sub.5 H.sub.11                                                                      2       78      72                                         25         C.sub.7 H.sub.15                                                                      2       88      79                                         26         C.sub.7 H.sub.15                                                                      3       87      77                                         27         C.sub.8 H.sub.17                                                                      2       89      81                                         28         C.sub.9 H.sub.19                                                                      1       88      80                                         29         C.sub.9 H.sub.19                                                                      2       89      78                                         30         C.sub.9 H.sub.19                                                                      4       87      78                                         31         C.sub.11 H.sub.23                                                                     3       92      82                                         32         C.sub.13 H.sub.27                                                                     2       90      79                                         33         C.sub.15 H.sub.31                                                                     2       91      78                                         34         C.sub.15 H.sub.31                                                                     4       90      80                                         35         C.sub.17 H.sub.35                                                                     1       88      76                                         36         C.sub.19 H.sub.39                                                                     2       74      61                                         37         C.sub.19 H.sub.39                                                                     3       72      60                                         ______________________________________                                    

As seen very good results are obtained in examples 24 to 35, while therate of mineral recovery has decreased in examples 22, 23, 36 and 37.That means best collectors are those in which R is an alkyl of C₅ to C₁₇or--in other words--the thioamide group R--CS--NH-- has 6 to 18 carbonatoms.

EXAMPLES 38-44

Flotation tests, similar to those of preceding examples, were carriedout with different thioamides having two OH in their substitution group.They are characterized by the formula ##STR28##

The following recovery rates were obtained.

    ______________________________________                                        Example     Alkyl          % of mineral recovered                             N°  R       n       galena  blende                                     ______________________________________                                        38         C.sub.3 H.sub.7                                                                       2       66      61                                         39         C.sub.5 H.sub.11                                                                      2       80      74                                         40         C.sub.9 H.sub.19                                                                      1       90      81                                         41         C.sub.9 H.sub.19                                                                      2       91      83                                         42         C.sub.9 H.sub.19                                                                      3       89      80                                         43         C.sub.17 H.sub.35                                                                     3       90      78                                         44         C.sub.19 H.sub.39                                                                     2       73      63                                         ______________________________________                                    

While the above results show that the presence of a second OH in themolecule of thioamide somewhat improves the flotation, they confirm theconclusion from examples 21-37 that commercially best collectors arethose in which R has 5 to 17 carbon atoms.

EXAMPLES 45-49

Flotation experiments were carried out with a fine powder of a mineral90% of which pass the US sieve n° 140 (ASTM E-11-61), that means havedimensions less than 105 microns. The mineral originated from FrenchPyrenean region and had 4, 8% Pb and 12, 1% Zn in sulfide from.

The powder is froth flotated during 15 minutes in an industrialflotation cell of 125 liters. The pH of the pulp treated is 7.5. 25grams of methyl isobutyl carbinol per ton of mineral are added asfoaming agent. Each of the collectors studied is used at the rate of0.132 moles per ton of mineral; the corresponding amounts expressed ingrams per ton (g/t) are given in the following Table of results, whichshows the % of Pb and Zn recovered.

    ______________________________________                                        Ex.  collector          g/t    % Pb   % Zn                                    ______________________________________                                        45   C.sub.11 H.sub.23 CSNHCH.sub.2 CH.sub.2 OH                                                       35     92.4   82.8                                         N--(2-hydroxyethyl)                                                           thiododecanamide                                                         46   C.sub.9 H.sub.19 CSNHCH.sub.2 CH(OCH.sub.3).sub.2                                                35     91.3   83.9                                         N--(2,2-dimethoxyethyl)                                                       thiodecanamide                                                           47   C.sub.9 H.sub.19 CSNHCH.sub.2 CH.sub.2 OC.sub.2 H.sub.5                                          33     90.7   83.5                                         N--(2-ethoxyethyl) thio-                                                      decanamide                                                               48   C.sub.11 H.sub.23 CSN(CH.sub.2 CH.sub.2 OH).sub.2                                                40     93.2   86.1                                         N--bis (2-hydroxyethyl)                                                       thiododecane-amide                                                       49   Potassium amyl-    20     86.7   78.8                                         xanthate: "PAX"                                                          ______________________________________                                    

As seen the collectors according to the invention, 45 by 48, give quitebetter results than one of the best usual collectors, the PAX, does.

EXAMPLE 50

The compound of example 45, that means C₁₁ H₂₃ CSNHCH₂ CH₂ OH has beentested as froth flotation collector in a Halimond cell following theprocedure described in U.S. Pat. No. 4,274,950, col.3, with a mineralwhich contains galena, blende, chalcopyrite and pyrite. The flotation iseffected with pulps having different pH.

Here are the rates of recovery of each of the above minerals.

    ______________________________________                                               % recovered                                                            pH       Galena  Blende    Chalcopyrite                                                                           Pyrite                                    ______________________________________                                        5.5      94      87        68       36                                        7.5      93      81        57       52                                        9.0      89      28        53       21                                        10.5     82      21        50       12                                        ______________________________________                                    

EXAMPLE 51

By the same method as in Example 50,N-(2,2-dimethoxyethyl)thiodecanamide, i.e. C₉ H₁₉ CSNHCH₂ CH₂ (OCH₃)₂ istried as collector. The following results are obtained.

    ______________________________________                                               % recovered                                                            pH      Galena  Blende     Chalcopyrite                                                                           Pyrite                                    ______________________________________                                        5.5     89      58         78       44                                        7.5     86      44         69       28                                        9.0     83      22         62       27                                        10.5    82      18         59       22                                        ______________________________________                                    

The above examples show that it is possible to choose a collectoraccording to the invention and use it at an appropriate pH, that certainof the mineral components be enriched with respect to others.

What is claimed is:
 1. Process of froth flotation of metal sulfideminerals in which a thioamide is employed as the collector and the metalsulfide is recovered from the froth, wherein the thioamide is of theformula ##STR29## R designating C₅ to C₁₇ alkyls, R' being H or(CH₂)_(n) OR" and n an integer of 1 to 6, while Z is --OR" or ##STR30##where R" means H, CH₃ or C₂ H₅.
 2. Process according to claim 1, whereinthe collector is N-(2-hydroxyethyl)-thiodecanamide.
 3. Process accordingto claim 1, in which the collector is N-(2-hydroxyethyl)-thiodecanamide.4. Process according to claim 1, in which the collector isN-bis(2-hydroxyethyl)-thiodecanamide.
 5. Process according to claim 1,in which the collector is N-(2-methoxyethyl)-thiodecanamide.
 6. Processaccording to claim 1, in which the collector isN-(2,2-dimethoxyethyl)thiodecanamide.
 7. Process according to claim 1,in which the collector is N-(2-methoxyethyl)-thiodecanamide.
 8. Processaccording to claim 1, in which the collector isN-bis(2-methoxyethyl)-thiodecanamide.
 9. Process according to claim 1,wherein n is 1 or
 2. 10. Process according to claim 9, wherein R is a C₇to C₁₁ linear alkyl.
 11. Process according to claim 10, wherein R" is H.12. Process according to claim 10, wherein R" is CH₃.